EP0075559B1 - A method and apparatus for functionally testing a laser rangefinder - Google Patents

A method and apparatus for functionally testing a laser rangefinder Download PDF

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Publication number
EP0075559B1
EP0075559B1 EP82900840A EP82900840A EP0075559B1 EP 0075559 B1 EP0075559 B1 EP 0075559B1 EP 82900840 A EP82900840 A EP 82900840A EP 82900840 A EP82900840 A EP 82900840A EP 0075559 B1 EP0075559 B1 EP 0075559B1
Authority
EP
European Patent Office
Prior art keywords
voltage
laser
finder
pulse
light pulses
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82900840A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0075559A1 (en
Inventor
Karl Helmer Johansson
Anders Stefan Severinsson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of EP0075559A1 publication Critical patent/EP0075559A1/en
Application granted granted Critical
Publication of EP0075559B1 publication Critical patent/EP0075559B1/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4008—Means for monitoring or calibrating of parts of a radar system of transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/4808—Evaluating distance, position or velocity data
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/484—Transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/497—Means for monitoring or calibrating

Definitions

  • the invention described here relates to a method and apparatus for functionally testing a laser rangefinder, all in accordance with the preambles of the following independent claims.
  • Rangefinders based on measuring the time taken for a light pulse from a laser in the range- finder to reach an object, the distance to which shall be measured, and return to the instrument after reflection by the object are tested for correct function and precision using a known measuring distance. Testing can therefore only be carried out at places which are specially arranged for the purpose.
  • a laser of the passive Q-switched laser type can transmit more than one light impulse when the laser excitation voltage is higher than normal. This is a drawback with this type of laser, since normally it is only desired to transmit one light pulse at each measuring occasion.
  • the property which is otherwise regarded as a drawback of the passive Q-switched laser has been taken advantage of, namely that it transmits two light pulses when the laser excitation voltage is raised above the normal value.
  • Each transmitted light pulse is reflected in a mode known per se to the rangefinder receiver, the first such pulse starting time measurement and the second one stopping it in the same way as a light pulse reflected from a remote object would also do.
  • a voltage divider in a control circuit controlling the excitation voltage is adapted for switching by a switch especially arranged for testing.
  • the invention is not intended for testing the precision of the distance measurement, since such testing still requires specially prepared measuring distances.
  • the rangefinder laser is of the passive Q-switched type.
  • the rangefinder laser is adapted to transmit a short light pulse when it is struck by a light flash from the rangefinder flashlamp 1.
  • Energy for the flashlamp is supplied by a charging capacitor C1 in series with the flashlamp 1.
  • a choke L is also connected in series in the same circuit with said components.
  • the capacitor C1 is connected to a high-voltage unit 2 for charging, the unit being disposed for receiving a DC supply on two terminals 3.
  • the output of a regulating amplifier 4 is connected to the high-voltage unit for controlling its output voltage.
  • a constant reference voltage is connected to one input of the amplifier, and to a second input thereof is connected a point of a voltage divider comprising three resistors R1, R2 and R3. The voltage divider is connected between the pole with the high voltage U and the other earthed pole of the high-voltage unit.
  • a switch 5 is coupled across the resistor R3, which is nearest the earthed side of the voltage divider, for short-circuiting the resistor 3 when closed.
  • a pulse transformer 6, in this connection called a triggering transformer, has one winding connected to one of the poles of the flashlamp 1.
  • the second winding of the transformer is included in a circuit where the winding is in series with a capacitor 7 and a thyristor 8.
  • the thyristor is adapted to be made conductive by a voltage pulse on a connection 9 connected to the thyristor 8.
  • the capacitor 7 is intended for charging by a DC source connected to both terminals 10.
  • the described apparatus is made ready for actuating the laser in the rangefinder to give one or more light pulses by direct voltage being applied to the terminals 3, so that the capacitor C1 is charged to high voltage by the high-voltage unit 2.
  • the voltage divider R1, R2, R3 leads a part of the voltage U to one of the inputs on the regulating amplifier 4.
  • the voltage U is kept to a value such that the voltage fed back from the voltage divider to the amplifier will equal that of the constant voltage REF.
  • the capacitor 7 coupled to the triggering transformer 6 is also charged.
  • the apparatus is now ready to release light pulses from the laser.
  • the thyristor 8 is made conductive by a direct voltage connected to the terminal 9.
  • the capacitor 7 is then discharged by a current shock to one winding of the triggering transformer 6.
  • In the second winding thereof there is induced a high voltage at its free pole 11, which then gives rise to an electric field adapted for actuating the flashlamp 1.
  • a flash is thus released in the flashlamp and the charge of the capacitor C1 is discharged in a current through the lamp.
  • the flash from the flashlamp actuates the laser to transmit a light pulse.
  • the voltage U across the capacitor C1 has namely been just high enough, and the flash from the flashlamp just strong enough, for the laser to give a sole light pulse.
  • the apparatus is instead made ready to give a flash pulse with the switch 5 closed, the portion of the voltage U which is fed back to the amplifier 4 will be less than before, the voltage being regulated to a higher value than in the former case.
  • the voltage U in this case is selected sufficiently high for the flash from the flashlamp 1 to be strong enough for the laser to give two light pulses within a short time interval.
  • the rangefinder optics are disposed for reflecting to its light receiver a small portion of the light in the pulses sent by the laser. As always, the reflection of the light pulse first sent starts the time measurement of the rangefinder. Reflection of the second light pulse sent from the laser is recognized in the rangefinder in the same way as a pulse reflected from a target, and will stop the time measurement. The time interval from start to stop is recalculated as a distance.
  • the range- finder can transmit laser pulses, that its light receiver can receive reflected laser radiation, and that its time measurement circuits are functional and can indicate a distance.
  • the voltage across the capacitor C1 is selected such that the time interval between both light pulses is nominally 30 ⁇ s, corresponding to a measuring distance of 4500 meters.
  • Other settings of the time interval and measuring distance are naturally possible also.
  • the time interval on different occasions can vary up to ⁇ 20 percent, the functional test is therefore not suitable for checking the accuracy of the rangefinder, but solely for checking its correct function.
  • the resistor R3 and the switch 5 have been added, the remaining components in the described apparatus normally being associated with the laser range- finder.
  • the resistor R3 is built into the range- finder, while the switch 5 is accommodated in a special auxiliary testing unit which can be connected to the rangefinder with a connection means 12.
  • the switch 5 can be built into the rangefinder and disposed for resetting by means of a push button on the rangefinder.
  • the operation of the function tester is based on the property of the passive Q-switched laser that when the voltage U on the capacitor C1 is within a given range, the laser sends a single light pulse when the capacitor is discharged, while when the voltage U is increased, the laser sends more than one light pulse, the number of light pulses for increasing U increasing to two, three and even more.
  • the laser sends more than one light pulse, the number of light pulses for increasing U increasing to two, three and even more.
  • for a laser to send more than one light pulse is often a drawback, but in the method and apparatus for functional testing the otherwise undesired property of the laser has been turned to advantage.
  • Test apparatus provided with means equivalent to those described are also regarded as being embraced by the following claims.
  • the voltage divider can be made with capacitors instead of resistors.

Landscapes

  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optical Radar Systems And Details Thereof (AREA)
  • Measurement Of Optical Distance (AREA)
  • Length Measuring Devices By Optical Means (AREA)
EP82900840A 1981-03-25 1982-03-16 A method and apparatus for functionally testing a laser rangefinder Expired EP0075559B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8101919A SE425702B (sv) 1981-03-25 1981-03-25 Forfarande och anordning for att funktionsprova en laseravstandsmetare
SE8101919 1981-03-25

Publications (2)

Publication Number Publication Date
EP0075559A1 EP0075559A1 (en) 1983-04-06
EP0075559B1 true EP0075559B1 (en) 1985-10-30

Family

ID=20343433

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82900840A Expired EP0075559B1 (en) 1981-03-25 1982-03-16 A method and apparatus for functionally testing a laser rangefinder

Country Status (10)

Country Link
US (1) US4552455A (da)
EP (1) EP0075559B1 (da)
DE (1) DE3267095D1 (da)
DK (1) DK153184C (da)
ES (1) ES8303710A1 (da)
FI (1) FI75234C (da)
NO (1) NO154507C (da)
SE (1) SE425702B (da)
WO (1) WO1982003463A1 (da)
YU (1) YU43723B (da)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1984004658A1 (fr) * 1983-05-27 1984-12-06 Philippe Billet Combinaison blaireau - reservoir de creme a raser
US5214483A (en) * 1992-08-06 1993-05-25 The United States Of America As Represented By The Secretary Of The Navy Digital laser range finder emulator
US5343483A (en) * 1993-03-19 1994-08-30 Wisconsin Alumni Research Foundation High voltage fast pulse control for a Q-switched laser

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL131544C (da) * 1965-02-03
US3545862A (en) * 1968-01-26 1970-12-08 Eg & G Inc Multi-pulse laser ranging system
FR1587762A (da) * 1968-09-27 1970-03-27
SE362504B (da) * 1972-05-02 1973-12-10 Bofors Ab
FR2398314A1 (fr) * 1977-07-21 1979-02-16 Cilas Dispositif pour mesurer une composante de la vitesse du vent

Also Published As

Publication number Publication date
FI823946L (fi) 1982-11-17
FI75234C (sv) 1988-05-09
NO823945L (no) 1982-11-24
DE3267095D1 (en) 1985-12-05
YU43723B (en) 1989-10-31
FI75234B (fi) 1988-01-29
DK519882A (da) 1982-11-22
NO154507B (no) 1986-06-23
ES510735A0 (es) 1983-02-01
YU63382A (en) 1985-03-20
US4552455A (en) 1985-11-12
ES8303710A1 (es) 1983-02-01
NO154507C (no) 1986-10-01
EP0075559A1 (en) 1983-04-06
FI823946A0 (fi) 1982-11-17
DK153184C (da) 1988-11-07
WO1982003463A1 (en) 1982-10-14
DK153184B (da) 1988-06-20
SE425702B (sv) 1982-10-25
SE8101919L (da) 1982-09-26

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